Inserting a POJO with a JsonNode field into MongoDB using Java driver

Question

Im using Mongo Java driver 3.7

This is my POJO(with getters and setters) -

public class Sample{
    public int field1;
    public JsonNode field2;
}

Im using the below code to insert an object of Sample into MongoDB.

MongoCollection<Sample> myCollection = database.getCollection("myCollection",Sample.class);
ObjectMapper mapper = new ObjectMapper();
    Sample obj = new Sample();
    obj.setField1(1);
    String sampleJSON = "{ \"key\": \"value\" }";
    obj.setField2(mapper.readTree(sample));

myCollection.insertOne(obj);

Seen Output: (JsonNode field is empty)

{
    "_id" : ObjectId("5afbff8a8f621e1e328a8c4e"),
    "field1" : 1
    "field2" : [
                 [ ]
               ],
}

Note: In debug mode, it is clear that the JsonNode is created with proper data. But insert is misbehaving. I guess I'm missing something here. Any leads appreciated.

Update: I tried writing a custom codec for JsonNode class, but it is never being used by mongo. This is my codec code -

@Slf4j
public class JsonNodeCodec implements CollectibleCodec<JsonNode> {
    @Inject
    private ObjectMapper objectMapper;

    @Override
    public JsonNode generateIdIfAbsentFromDocument(JsonNode jsonNode) {
        return null;
    }

    @Override
    public boolean documentHasId(JsonNode jsonNode) {
        return false;
    }

    @Override
    public BsonValue getDocumentId(JsonNode jsonNode) {
        return null;
    }

    @Override
    public JsonNode decode(BsonReader reader, DecoderContext decoderContext) {
        String task = reader.readString();
        JsonNode node = objectMapper.readTree(task);
        return node;
    }

    @Override
    public void encode(BsonWriter writer, JsonNode jsonNode, EncoderContext encoderContext) {
        writer.writeString(jsonNode.toString());
    }

    @Override
    public Class<JsonNode> getEncoderClass() {
        return JsonNode.class;
    }
}

And I'm registering the codec like this -

Codec<JsonNode> jsonNodeCodec = new JsonNodeCodec();
CodecRegistry codecRegistry = CodecRegistries.fromRegistries(com.mongodb.MongoClient.getDefaultCodecRegistry(),
            CodecRegistries.fromCodecs(jsonNodeCodec),
            CodecRegistries.fromProviders(PojoCodecProvider.builder().automatic(true).build())
    );

PS: Other codecs registered for custom POJOs are working fine. But this codec is never being used to encode/decode JSON objects

Rajat Goel · Accepted Answer · 2020-05-14 06:22:17Z

5

Just add custom converters to convert JsonNode object to org.bson.Document and vice-versa. Keep your POJOs/Document classes as it is with JsonNode fields. If using spring :

@Bean
public MongoCustomConversions mongoCustomConversions() {
    List<Converter<?, ?>> converters = new ArrayList<>();
    converters.add(JsonNodeToDocumentConverter.INSTANCE);
    converters.add(DocumentToJsonNodeConverter.INSTANCE);
    return new MongoCustomConversions(converters);
}

@WritingConverter
enum JsonNodeToDocumentConverter implements Converter<JsonNode, Document> {
    INSTANCE;

    public Document convert(JsonNode source) {
        if(source == null)
            return null;

        return Document.parse(source.toString());
    }
}

@ReadingConverter
enum DocumentToJsonNodeConverter implements Converter<Document, JsonNode> {
    INSTANCE;

    public JsonNode convert(Document source) {
        if(source == null)
            return null;

        ObjectMapper mapper = new ObjectMapper();
        try {
            return mapper.readTree(source.toJson());
        } catch (IOException e) {
            throw new RuntimeException("Unable to parse DbObject to JsonNode", e);
        }
    }
}

edited May 14, 2020 at 6:22

answered May 12, 2020 at 12:21

Rajat Goel

2,3051 gold badge20 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

jka Over a year ago

Will this just add two more converters to list existing default converters? Or this replaces all converters with two total converters?

Rajat Goel Over a year ago

Will add two more, Default constructor is MongoCustomConversions() { this(Collections.emptyList()); }

Konstantin Ziubin Over a year ago

Why you use singletons for converters?

Somil Aseeja · Accepted Answer · 2018-08-27 10:15:58Z

2

I was facing the same issue here and resolved using ObjectMapper.

Use below:

ObjectMapper mapper =   new ObjectMapper();
Map inputMap        =   mapper.convertValue(jsonNode, Map.class);

answered Aug 27, 2018 at 10:15

Somil Aseeja

17010 bronze badges

Collectives™ on Stack Overflow

Inserting a POJO with a JsonNode field into MongoDB using Java driver

2 Answers 2

3 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related